1. Field of the Invention
The present invention relates to a touch sensing system and a driving method thereof and, more particularly, to a touch sensing system and a driving method thereof which improves touch sensitivity by sensing small change in sensing signals upon movement of touch by a user.
2. Description of the Related Art
The touch screen is an input apparatus for inputting a user's command by selecting an instruction content displayed on a screen of an image display apparatus and the like by a human's hands or an object.
To this end, the touch screen is positioned on a front face of the image display apparatus for converting a contact position directly contacted with a human's hands or an object into electrical signals. Accordingly, the instruction content selected at the contact position is received as input signals.
Since such a touch screen may replace separate input apparatuses, such as a keyboard and a mouse, to be connected to and operated with the image display apparatus, the range of its use has grown.
Types of arrangements for implementing the touch screen have included a resistive film type, an optical sensing type, a capacitance type, and the like.
Of these, the touch screen of the capacitance type detects touch positions by detecting change in the capacitance produced when a person's hands or objects contact the touch screen, and to this end, the touch sensing system is provided to detect the coordinates of the touch positions by analyzing the sensing signals outputted from a number of sensing electrodes.
That is, when the difference values between the sensing signals and the baselines are larger than predetermined reference values, it is determined that the touch of the user exists on the touch sensing system.
When there are no user inputs by fingers and there is also no influence of external noise, the values sensed by the touch sensing unit are constant, and the constant values are called baselines. That is, the baselines are basic input values which exists in the absence of any input on the touching sensing unit. Here, noise refers to unwanted signals that occur in the system due to electrical and mechanical causes.
In a touch sensing system of the related art, the baselines are updated to keep up with the sensing signal values changed by noise so as to minimize influence of the noise when the touch is absent, and the updating of the baselines stops when the touch is present, thereby detecting the difference between the sensing signals and the baselines.
However, in the case of moving after touching by the user without detaching fingers, there is a problem in that it is not recognized as a touch.